1. Field
The present disclosure relates to the compression of data and, more particularly, to the compression of video data based at least upon a variable bit rate compression scheme.
2. Background Information
The control of video bit rate—the number of bits per second used to encode a video data—is an important issue in the field of digital video compression. Generally there are two kinds of bit rate control schemes, constant bit rate (CBR) and variable bit rate (VBR) control.
A CBR control scheme generally allocates a constant amount of bits to each frame or picture in video data. Some CBR schemes may subdivide the video data into a series of groups of pictures (GOPs) and allocate a constant amount of bits to represent each GOP. One of the advantages of a CBR scheme is that the allocation of bits is simple. One of the disadvantages of a CBR scheme is that the quality of the resulting compressed video data may vary as a function of the complexity of each GOP. If a GOP is complex, for example, it may contain a large number of colors, or a lot of motion, and, therefore, require a relatively large number of bits to capture the complexity of the GOP without an unacceptable loss of information. Conversely, a simple GOP requires a relatively low number of bits to capture the simplicity of the GOP, and, therefore, an excess number of bits may be used to encode the GOP. Because, under a CBR scheme, the same number of bits is used to represent both a highly complex GOP and a very simple GOP, the percentage of information that is captured in the compressed video data varies based on the complexity of the GOP. As a result, a user typically perceives the compressed video data as varying in quality through the video.
A VBR control scheme typically breaks video data into a series of groups of pictures. Each GOP is allocated a different number of bits depending upon the complexity of the GOP. A VBR scheme typically results in higher video quality than a CBR scheme because, as the complexity of the video data increases, the number of bits used to represent the video may increase. However, the quality of the resulting compressed video data is often dependent upon the ability of the VBR scheme to allocate a proper number of bits to the GOP. If the VBR scheme allocates too many bits the quality of the video may be high, but the size of the compressed video data may increase unnecessarily. If the VBR scheme allocates too few bits, the size of the compressed video data may be small, but quality of the video may decrease.